In various applications it is necessary or desirable to provide a resilient rotary bias device for maintaining continuous rotary "tension" on a shaft; the bias device is usually expected also to function as a shock absorber in those instances in which the shaft may be subject to a force exceeding the bias level. Resilient rotational bias devices of this general type can be used in some forms of exercise equipment. Another appropriate application for a rotary resilient bias device is on the operating shaft of a conveyor belt scraper, either a primary scraper or a secondary scraper.
In some of these applications, it is necessary or desirable to provide some arrangement for adjusting the rotary biasing force applied by the device to a shaft or other like member. Frequently, this is done with set screws that are released to permit setting of the rotational bias force to be exerted by the device. An example of an apparatus of this kind is presented in Swinderman et al. U.S. Pat. No. 4,925,434. Another apparatus used for this purpose, employing a pin and key connection between the shaft and the resilient rotary bias device, is described in Gordon U.S. Pat. No. 4,533,036. Known arrangements of this kind, however, have required a change of bias in discrete steps; thus, they have not permitted adjustment of the bias force to any desired level within a given range, on a continuous basis. Moreover, the set screws and other fasteners employed in apparatus of this kind have sometimes been unsatisfactory from the standpoint of corrosion and have a tendency to adhere to the other components of the apparatus, particularly in conveyor belt cleaners when used in adverse environmental conditions as may be encountered in mines, power plants, and even in food processing establishments.